I know this is not about cast bullets, but it is related to guns and a lot of us here are DIY-ers, so I thought it might be of interest....
Most people know that wood shrinks as it dries/ages. For lumber, most of this shrinkage happens during the kiln-drying process, so we don’t tend to think about it much. For rifle-builders, stock blanks are commonly aged for a couple of years to give them adequate time to stabilize (i.e. shrink) before carving. We’ve all seen warped and twisted lumber down at the lumber yard, and probably thought, “Oh, it must have gotten rained on.”, but is that really what caused it?
The drying of wood is both a simple and a complex process. When a tree is cut down, it contains a large amount of water in both the vascular and cellular structure of the wood. After the log is cut into lumber, the drying process allows some of this water to evaporate. Due to the open nature of the vascular (pore) structure of the wood, this water content comes out fairly quickly and easily. The water contained in the cellular structure of the wood is more tightly constrained, and comes out more slowly.
Water takes up volume, so as wood dries it shrinks. If you’ve ever seen raw lumber dry out, you’ve seen some of this shrinkage first hand – the piece of wood physically gets smaller (up to a point). After a while, this dimensional shrinkage stops, and the outer dimensions of the wood become stable. Is the wood completely dried out at this point? No! There is still water in there, and the drying process continues (albeit more slowly). Beyond this point, when the water leaves, there are two things that happen – 1. Very small shrinkage cracks begin to form inside the wood, and 2. Small internal stress/strain fields begin to form in the wood (similar to those encountered in metallurgy and glass chemistry).
99+% of the time we completely ignore these effects because usually when we are working with wood we are cutting 2x4s to frame up a backyard garden shed or a tree-house, and all we are really interested in is dimensional stability to about +/- 1/8” (.125”). More demanding applications, like cabinet making or furniture building, still only require dimensional precision of about +/- 1/32” (over .030”). Very few applications that we use wood for require precision tolerances of +/- .001” or .002”, so warpage or change in dimensions of .005”, or even .010”, are generally completely ignored, and we go merrily on our way and frame up our new deck, or build our new gun rack, oblivious to the warpage/shrinkage taking place beneath our very fingers.
Making handgun grips can be a little different though. Many types of grips are pretty straightforward – like 1911s, Ruger single-actions, S&W Magnas, etc. These grips are all what I call flat-backed grips in that they all index off of a single plane that abuts directly on a rigid steel frame. Any minor warpage (minor meaning a few thousandths) in the grips can be overcome by the compressive force of the mounting screw, so all seams and interfaces are sucked up nice and tight.
But fancier grips, like finger-groove grips or grips that fill in on the backside of the trigger guard involve a clamshell design that requires the recess for the gripframe be milled out (as well as recesses for the frame and trigger guard). Any time one cuts or mills wood, some internal stress/strain fields are being relieved, and others are not. This leads to warpage and/or dimensional changes. It’s not unusual, when milling these recess for portions to come out deeper or shallower than intended by a few thousandths. What’s more, as the part sits out overnight (or longer), it’s not unusual for these numbers to change over time as the wood stabilizes to its new configuration. Now in most cases, these changes are quite modest (a few thousandths), but I’ve seen a few isolated extreme cases where the changes were as much as .015” or .020”.
Why is this important? Well, where the two clamshell halves meet up (at the front and bottom of the grips), to make what I call the “belly seam”, if there is a gap left between the two grips, then it detracts from the appearance of the grips. Ideally, in a perfect world, right as the two grips came into firm contact with the gripframe, the belly seam would close up tight, with zero gap. Well, I’m sorry to break the news to you, but we don’t live in a perfect world. It’s not unusual for carefully milled out grip halves, when mated on the gripframe, to meet up snugly in places, and have gaps in others (this can even change over time). This is a due to the warpage/dimensional changes described above (it can also be due to drying if the wood is still fairly green). Again, usually these changes are on the order of a few thousandths, but sometimes it can be more. How much gap is too much? Well, beauty is in the eye of the beholder, and what may look just fine to one shooter may be absolutely unacceptable to another (personally, I aim for zero, and anything over .005” is generally unacceptable). The way I deal with this is to mill these recesses a little bit deeper than necessary, so the lips that come together to form the belly seam are actually a few thousandths taller than necessary. Since we don’t know where the high points and low points are going to come out after the warpage/dimensional changes, we also don’t know how they are going to mate up with those of the opposing grip. By making everything a little taller than spec, then we can put things together, and using a set of feeler gauges, and some very careful sanding techniques, close up this gap to near perfection. It takes time, and patience, but it results in better fit, and better looking grips.
I like to take this stabilization one step further – when making grips, I cut out the raw slabs that I will use to make a grip set, then mill and sand everything to square it up, then let those slabs sit for a week to stabilize (sometimes I have to re-mill them after this week). Then after I have milled the gripframe recesses, and cut the slabs to rough shape, I like to let them sit and stabilize for a few more days before I start shaping and contouring the outer surfaces. Then it’s time for sanding and finishing the grips and that’s when I start to think about fine-tuning the belly seam fit. This gives the wood lots of time settle in to its new configuration (“get the wiggles out”) and stabilize so I’m not chasing a moving target while fitting the belly seam.
Now if you’ll excuse me, I have some sanding to do….
Most people know that wood shrinks as it dries/ages. For lumber, most of this shrinkage happens during the kiln-drying process, so we don’t tend to think about it much. For rifle-builders, stock blanks are commonly aged for a couple of years to give them adequate time to stabilize (i.e. shrink) before carving. We’ve all seen warped and twisted lumber down at the lumber yard, and probably thought, “Oh, it must have gotten rained on.”, but is that really what caused it?
The drying of wood is both a simple and a complex process. When a tree is cut down, it contains a large amount of water in both the vascular and cellular structure of the wood. After the log is cut into lumber, the drying process allows some of this water to evaporate. Due to the open nature of the vascular (pore) structure of the wood, this water content comes out fairly quickly and easily. The water contained in the cellular structure of the wood is more tightly constrained, and comes out more slowly.
Water takes up volume, so as wood dries it shrinks. If you’ve ever seen raw lumber dry out, you’ve seen some of this shrinkage first hand – the piece of wood physically gets smaller (up to a point). After a while, this dimensional shrinkage stops, and the outer dimensions of the wood become stable. Is the wood completely dried out at this point? No! There is still water in there, and the drying process continues (albeit more slowly). Beyond this point, when the water leaves, there are two things that happen – 1. Very small shrinkage cracks begin to form inside the wood, and 2. Small internal stress/strain fields begin to form in the wood (similar to those encountered in metallurgy and glass chemistry).
99+% of the time we completely ignore these effects because usually when we are working with wood we are cutting 2x4s to frame up a backyard garden shed or a tree-house, and all we are really interested in is dimensional stability to about +/- 1/8” (.125”). More demanding applications, like cabinet making or furniture building, still only require dimensional precision of about +/- 1/32” (over .030”). Very few applications that we use wood for require precision tolerances of +/- .001” or .002”, so warpage or change in dimensions of .005”, or even .010”, are generally completely ignored, and we go merrily on our way and frame up our new deck, or build our new gun rack, oblivious to the warpage/shrinkage taking place beneath our very fingers.
Making handgun grips can be a little different though. Many types of grips are pretty straightforward – like 1911s, Ruger single-actions, S&W Magnas, etc. These grips are all what I call flat-backed grips in that they all index off of a single plane that abuts directly on a rigid steel frame. Any minor warpage (minor meaning a few thousandths) in the grips can be overcome by the compressive force of the mounting screw, so all seams and interfaces are sucked up nice and tight.
But fancier grips, like finger-groove grips or grips that fill in on the backside of the trigger guard involve a clamshell design that requires the recess for the gripframe be milled out (as well as recesses for the frame and trigger guard). Any time one cuts or mills wood, some internal stress/strain fields are being relieved, and others are not. This leads to warpage and/or dimensional changes. It’s not unusual, when milling these recess for portions to come out deeper or shallower than intended by a few thousandths. What’s more, as the part sits out overnight (or longer), it’s not unusual for these numbers to change over time as the wood stabilizes to its new configuration. Now in most cases, these changes are quite modest (a few thousandths), but I’ve seen a few isolated extreme cases where the changes were as much as .015” or .020”.
Why is this important? Well, where the two clamshell halves meet up (at the front and bottom of the grips), to make what I call the “belly seam”, if there is a gap left between the two grips, then it detracts from the appearance of the grips. Ideally, in a perfect world, right as the two grips came into firm contact with the gripframe, the belly seam would close up tight, with zero gap. Well, I’m sorry to break the news to you, but we don’t live in a perfect world. It’s not unusual for carefully milled out grip halves, when mated on the gripframe, to meet up snugly in places, and have gaps in others (this can even change over time). This is a due to the warpage/dimensional changes described above (it can also be due to drying if the wood is still fairly green). Again, usually these changes are on the order of a few thousandths, but sometimes it can be more. How much gap is too much? Well, beauty is in the eye of the beholder, and what may look just fine to one shooter may be absolutely unacceptable to another (personally, I aim for zero, and anything over .005” is generally unacceptable). The way I deal with this is to mill these recesses a little bit deeper than necessary, so the lips that come together to form the belly seam are actually a few thousandths taller than necessary. Since we don’t know where the high points and low points are going to come out after the warpage/dimensional changes, we also don’t know how they are going to mate up with those of the opposing grip. By making everything a little taller than spec, then we can put things together, and using a set of feeler gauges, and some very careful sanding techniques, close up this gap to near perfection. It takes time, and patience, but it results in better fit, and better looking grips.
I like to take this stabilization one step further – when making grips, I cut out the raw slabs that I will use to make a grip set, then mill and sand everything to square it up, then let those slabs sit for a week to stabilize (sometimes I have to re-mill them after this week). Then after I have milled the gripframe recesses, and cut the slabs to rough shape, I like to let them sit and stabilize for a few more days before I start shaping and contouring the outer surfaces. Then it’s time for sanding and finishing the grips and that’s when I start to think about fine-tuning the belly seam fit. This gives the wood lots of time settle in to its new configuration (“get the wiggles out”) and stabilize so I’m not chasing a moving target while fitting the belly seam.
Now if you’ll excuse me, I have some sanding to do….
Last edited: